MONOTHEISM IN ISLAM
Monotheism is the message that all of the Prophets came with. People then deviated from the truth. Then Prophet Muhammad (peace be upon him) came as the final Messenger and restored true monotheism to humanity. Below is a detailed explanation of monotheism in Islam. You may compare it with concept of monotheism advanced by other religions.
Monotheism is the message that all of the Prophets came with. People then deviated from the truth. Then Prophet Muhammad (peace be upon him) came as the final Messenger and restored true monotheism to humanity. Below is a detailed explanation of monotheism in Islam. You may compare it with concept of monotheism advanced by other religions. 
The Arabic word ‘Tawheed’is generally translated in English as Monotheism. The term is derived from the three consonants root w-h-d, which serves as the vehicle for the basic concept of ‘oneness,’ or ‘unity,” along with the closely related ideas of ‘singularity’ and ‘uniqueness.’ These root letters are clearly apparent in the numerical adjective wahid [one]. In the words of the Qur`an:“inna Ilaaha-kum-la-Wahid”, Verily, your Ilah (God) is indeed One (i.e. Allah);.Qur’an.Surah Saffath 37:4
Based on the teachings of Qur’an and Sunnah, Tawheed can be classified as:
Monotheism forms the basis of Islam, one cannot enter into Islam without proclaiming that he believes in one Creator, who is unique and who is the Sustainer and Maintainer of everything that exists. He has the Divine power and nothing happens without His will.
Allah (Glory be to Him) is one without partners, children, or associates. He is the Most Merciful, the Most Wise, and the Most Just. He hears all things, sees all things and knows all. He is the only one who is worthy to be worshipped.
Qur’an.Surah.Al-Ikhlas Surah No. 112defines monotheism in the best way. It answers the most fundamental question, who should we worship and who can qualify to be God.
The surah is articulated in the Qur’an in this way (translation of the meanings): “Say, He is Allah, (Who is) One. Allah, the self-sufficient. He did neither beget and nor is He begotten. And there is none comparable unto Him.”
God bears witness that there is no god except He, and so do the angels and those who possess knowledge. Qur’an.Surah Al Imran 3:18.
You shall know that: “ There is no other god beside God, and ask forgiveness of your sins and the sins of all believing men and women. God is fully aware of your decisions and your ultimate destiny.” Qur’an.Surah Muhammad 47:19
Say, “God has proclaimed the truth: you shall follow Abraham’s religion- monotheism. He never was an idolater.” Qur’an.Surah Al Imran 3:95
The three types of tawhid, it can seen that the outward tawhid al-ibada refers to our actions, while tawhid ar-rububiyya and tawhid al-asma wa as-sifat refer to our knowledge and understanding, and the inner tawhid al-ibada refers to our motivations.
In other words, in order to be truly monotheistic, you must not only worship God alone in your prayer (outward tawhid al-ibada) but you must have the correct knowledge (tawhid ar-rububiyya), the correct understanding (tawhid al-asma wa as-sifat), and the correct motivation (inner tawhid al-ibada).